Oil burners



. 1958 J. w. BROWN :11 ETAL 2,857,961

OIL BURNERS Filed July 15, 1954 VFIGQI' ATTORNEIS United States Patent 2,857,961 7 on. BURNERS John W. Brown III, Lakewood, and Arvid C. K. Nihlen, Oberlin, Ohio, assignors to Brown Fintube Company, Elyria, Ohio, a corporation of Ohio Application July 13, 1954, Serial No. 443,026

1 Claim. (Cl. 1523-76) This invention relates to fuel burners and more particularly to high capacity burners adapted especially for liquid fuels, although they may also be used for burning gaseous fuels.

. A general object of the present invention is the provision of a compact, eflicient burner adapted to produce a high temperature flame, with efficient combustion and large thermal output in relation to the size of the burner.

Another object of the invention is the provision of such a burner which can readily be adapted to different purposes and uses. A further object is the provision of such a burner which can be started easily without the production of smoke or soot and which can be operated with a clean flame and eificient combustion from its full rated capacity down to approximately of its rated capacity. Another object is to provide a burner which can produce a reducing flame while still maintaining clean combustion. Another object is the provision of burners of this character than can be manufactured economically and which are of sturdy and dependable construction. A further object is the provision of burners which can be converted from liquid to gaseous fuel with a minimum of difliculty. Another object is the provision of burners in which the combustion process and the walls of the combustion chamber can be observed through a transparent wall of the burner.

More specific objects of the invention are the provision of burners especially adapted for use in regenerative ,1

furnaces, such as furnaces of the type utilized in the melting of glass and the provision of furnaces embodying such burners. Other objects and advantages of the invention will become apparent from the following description of preferred forms thereof, reference being made:v

Figure 1, the view being taken as indicated by line 22 of Figure 1.

Figure 3 is a front elevation of the burner shown in Figure 1, the view being taken as indicated by line 3-3 of Figure 1.

Referring now to Figures 1, 2 and 3 of the drawings, one preferred form of the invention comprises a cylindrical housing made up of a rear portion 10 and a front portion 11, these portions having matching flanges 12 and 13 that are bolted together as shown. The rear portion of the housing 10 constitutes an inlet or mixing chamber 15, the rear end of which is closed by a panel or plate 16 that is preferably composed of glass or a suitable transparent plastic material. Plate 16 is secured to the housing member 10 by bolts 17 extending through the. plate and through the rear flange 18 of the housing member. A supply pipe 20 for liquid fuel extends through an opening in plate 16 and is held in desired position of adjustment by set screw 21 mounted in block 22, which is secured to plate 16 by appropriate screws 23, as indicated in Figure 2. Fuel conduit 20 terminates in a spray nozzle 24 which has a number of small openings in its forward end 25 and is arranged to discharge finely divided fuel preferably in a narrow cone, as indicated by the broken lines in Figure 1; however, the shape of the cone is not critical, inasmuch as the oil particles are carried to the combustion zone by the air stream. Air to the mixing chamber 15 is supplied by a conduit 26 that extends through the wall of the rear housing member 10 as shown.

The forward wall of the mixing chamber 15 is defined by a conical member 30 which is welded to the forward end of the housing member '10 and converges in the direction of discharge of fuel and air from the mixing chamber. The small end of conical member 30 terminates in an aperture 31 which is concentric with the housing and with the axis of the nozzle 24. Preferab1y,. the opening 31 is surrounded bya short cylindrical lip or flange 32. This lip is preferably machined accurately to insure even distribution of the fuel and gases in the combustion zone.

Conical member 30 constitutes the :first cone of'a venturi which is completed by a secondconical member 34. Conical member 34 diverges in the direction of flow of gases in the burner; i. e., member 34 flares outwardly from the small opening 35 to the opening 36 at its discharge end. It will be noted that the opening 35 is slightly larger in diameter than the opening 31 of the converging conical member 30 and that the adjacent ends of the two members are axially spaced apart to provide an open throat 37 as shown.

The enlarged front end of the conical member 34 is supported from the forward housing member 11 by av perforated ring or spider 38 which acts as a flame holder and which is provided with a series of openings 39, as indicated particularly in Figures 1 and 3. Conical member 34 preferably terminates short of the discharge end of chamber 40 in the front housing member 11, as shown. With this arrangement, the flowof gases at high velocity through the venturi throat 37 defined by the small ends 31 and 35 of the converging cone 30 and the diverging cone 34 causes a reduction in pressure in the throat 37 with the result that hot products of combustion are drawn from the flame, which is held at the front end of cone 34 by the spider 38. The hot products of combustion are drawn rearwardly along the outside of cone 34 and into the venturi throat 37 and are recirculated through the combustion zone. The recirculated gas contains a substantial percentage of carbon monoxide inasmuch as combustion is not complete adjacent the spider. With this arrangement, cone 34 is maintained at a red heat after the burner has been in operation for a short time and the fuel is heated and partially volatilized as it passes through the cone. The result is a substantial increase in the rate of combustion as compared to combustion in conventional burners; the fuel can be burned substantially completely or a reducing flame can be produced by cutting down the supply of air; in either event the flame is clean and smokeless and there are substantially no deposits of carbon. In a successful burner embodying the invention having the general configuration shown in Figure 1, the total length of the housing is about 16 inches and the outside diameter of the housing is, about 6 inches. The included angle of cone 30 in this burner is approximately and the diameter of cone 30 at the throat is about 1 /2 inches. The small diameter of cone 34 is about 1% inches and the cone is about 7 inches long and 3 inches in diameter at its large end. With this arrangement the velocity of the gases through member 34 is approximately constant; i. e., the gases expand at about the same rate that the cross section of member 34 increases. Preferably, the gas velocity at the discharge end of member 34 is from 270 to 350 feet per second spanner} and about '10%'of'the gases arerecirculated, passing over the exterior of member 34 and in through the throat 37 of the venturi. This burner operates with an output of more than twomillion B. t. u. per hour 'andflame temperatures as'high as 3000" F. 'The flame temperature can-be variedyby changingthe gap 37 between cones gas, burner 42' which-extends through 'the wall of the "housing member'll andwhich may be supplied with'gas from a conduit-43L Thegas discharged from'burner 42 may be ignited by "means of any conventional spark igniter (not shown) and -gas'burner 42 is directed toward the throat of the venturi provided by cones 30 and 34. The burner preh'eats the cones 30 and 34 and the hot products ofcornbusti'on from the burner flow out through the cone '34. After the auxiliary burner 42 has been in operation 'for a few minutes, air may be supplied to the main burner through conduit 26 and liquid fuel may be "supplied to the nozzle 24. The spray of liquid fuel ignites immediately and clean and complete combustion begins at once. With thisjarrangement the heating effect of the gas burner'is'such that clean, complete and eflicient combustion of the liquid fuel can be obtained at rates as low as 10% of the maximum output of the burner. When'the burner is being used at its maximum output it is not necessary to supply fuel to the gas burner 42 but improved results and greater flexibility of operation are obtainedif the gas burner 42 is ignited when the main burner is operating at below 50% of rated capacity.

In order toprovide for'support for the entire burner a'flange'45jis secured to the forward end of the front housing member 11. This flange provides for mounting the burner on'the'heat exchanger or other'device with which it is to'be used. Mounting on the frontend only eliminates problems due to expansion and contraction of the burner under heat. The interior of the forward housing member 11 is lined with refractory insulating material tokeep the exterior of the burner cool-and prevent loss of heat from the recirculated gases.

The apparatus 'can be, adjusted for optimum results by sliding conduitj withinblock 22 to'adjust the position or the fuehnozzle, with respect to the throat of the venturi, and the length'of the venturi throat can be adjusted by inserting gaskets 48 of the proper thickness between the flanges 12 and 13. Since cone 30 is supported onthe-rear member 10 while cone 34is-supported -on the front housing member '11, changing the thickness of the gasket or gaskets 48 changes the spacing between the cones. Once the parts have been adjusted properly for a particular flame temperature, further adjustment is seldom necessary.

From the foregoing description of a preferred form of the invention, it will be seen that the invention provides a compact and efficient oil burner by means of which high thermal output and high temperatures'can be obtained in small spaces. Burners embodyingthe invention give clean and eflicient combustion and operate for long periods of time without requiring attention. The burners can-be operated at as low as 10% of their rated capacity while maintaining efficient operation and smoke free and soot free combustion. The burners are simple and sturdy and can be manufactured at reasonable cost. The burners are particularly'adapted 'to'use in regenerative furnaces or wherever preheated air is available.

Various changes and modifications in the preferred forms of the invention may bemade without departing frorn'thespirit and scope thereof. It-is, there-fore, to-be understood that the forms of the invention'described in detail herei'n'are given by way of example and that'th'e scope of the invention is defined by the appended-claim.

We claim: Abur'ner for fluid fuels comprising a housing having a rear portion defining -a mixing chamber, means for 'supplyi'ng'air'to the mixing chamber, a fuel conduit extending into-the mixing chamber and terminating in-a fuel nozzle, a converging conical member defi'ning'the forward, discharge end of the mixing chamber, "said conicalmember having a forward axial opening and said fuel nozzle'having a fuel discharge opening disposed to the rearof said axial opening, a diverging conical member-having an opening near but axially spaced from the opening in said converging conical member, said two conical members defining a venturi with an open throat,

References'Cited in the file of this patent UNIT ED STATES PATENTS 1,671,448 Plassmann- May 29, 1 928 1,699,732 Bal'mat Jan. 22, 1929 1,729,763 De Florez Oct. 1, 1929 1,737,681 Plassmann Dec. 3, 1929 2,701,608 Johnson Feb. 8,1955 

